The invention relates to a roll changer for splicing starting pieces and end pieces of material webs in an apparatus for producing hygienic products.
A method and an apparatus of the type of interest here are known in principle from EP 0 525 075 B1. This document describes a method and an apparatus for splicing at least two materials containing two single-ply or multi-ply, air permeable and soft paper webs. The material webs are joined by being spliced in the nip of two embossing rolls. The starting piece of the material web to be joined is initially held with the aid of a suction box, whose holding force is canceled when the web is to be joined to the end of piece of the other web.
The problem with the known apparatus is that it is necessary to operate there with a very accurately defined vacuum. Controlling the vacuum is therefore difficult. In addition, the fact that the end piece of one web has to pull the starting piece of the web to be joined to it is not without problems, although both webs, before entering the nip of the embossing rolls, are sucked against a suction box by vacuum.
The invention is therefore based on the object of providing the conditions for the most simple and quick roll change which may be carried out with only little effort.
In order to achieve this object, the invention provides, in a roll changer for splicing a starting piece to an end piece of successive material webs, for the starting piece of a new material web to be capable of being fixed to an embossing roll, and for at least one embossing roll to be capable of being driven and for at least one embossing roll to be capable of being moved toward the other embossing roll and away from it.
During production, the unwinding material web moves through the embossing nip without touching an embossing roll. Both embossing rolls are therefore stopped during production. According to the invention, the starting piece of the material web to be joined is fixed directly to one of the two stationary embossing rolls. For this purpose, both embossing rolls preferably have a suction strip or a row of suction openings and can be connected to vacuum lines.
In order to splice the materials webs, the two embossing rolls are pressed against each other and set rotating. In the process, the two material webs are joined by pressure and deformation in the manner of a splice, the end piece of one material web then being severed following the production of the splice.
The aforesaid measures can be prepared easily. The actual splicing operation can then be carried out securely and reliably. This results in a rapid roll change with a short transition from the end of one material web to the start of the next material web.